Re: [PATCH 2/2] ls-files: add --sparse option

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

On Wed, Dec 08 2021, Derrick Stolee wrote:

> On 12/8/2021 1:36 PM, Elijah Newren wrote:
>> On Wed, Dec 8, 2021 at 10:23 AM Derrick Stolee <stolee@gmail.com> wrote:
>>>
>>> On 12/8/2021 12:04 PM, Elijah Newren wrote:
>>>>
>>>> This actually looks quite nice, though the magic '16' is kind of
>>>> annoying.  Could we get rid of that -- perhaps using something to rip
>>>> out the diff header, or using comm instead?
>>>
>>> What I really want is "remove the first two lines of this file"
>> 
>> Is `tail -n +3` portable?  Looks like we have five uses of tail -n +N
>> in the testsuite, so it should be okay to use.
>
> Ah, that's the magic incantation. Sounds good.
>
>>> but perhaps "tail -n $(wc -l expect)" would suffice to avoid a
>>> magic number?
>> 
>> That works too.
>
> If the "-n +X" syntax works, then I'll opt for that.

I think it should be per
https://pubs.opengroup.org/onlinepubs/009695299/utilities/tail.html

But isn't that "diff -u" non-portable, per GIT_TEST_CMP. I.e. sometimes
we'll fall back on "cmp" etc.

Just pre-munging both "a" and "b" and doing a:

    test_cmp a b

Should work around that & make it portable.

I realize that's also a problem with my initial example, usually we'd
compare expected/actual, not the diff between the two.

But if that's more readable we could also just use "git diff --no-index
a b >actual" and "test_cmp" that v.s. "expected".